1. Field
One or more embodiments relate to a negative active material, a method of preparing the same, and a lithium battery including the negative active material, and more particularly, to a negative active material with improved capacity characteristics and ring lifetime characteristics, a method of preparing the same, and a lithium battery including the negative active material.
2. Description of the Related Technology
Secondary lithium batteries used in portable electronic devices for information communication, such as personal digital assistances (PDAs), mobile phones, or notebook computers, electric bicycles, electronic vehicles, etc. have a discharge voltage that is at least 2 times greater than those of conventional batteries and thus exhibit high energy density.
A secondary lithium battery includes a positive electrode, a negative electrode, and either an organic electrolytic solution or a polymer electrolytic solution filling a space between the positive and negative electrodes, wherein the positive and negative electrodes each include an active material that allows lithium ions to be intercalated and deintercalated. In this structure, when lithium ions are intercalated and deintercalated between the positive and negative electrodes, oxidation and reduction reactions occur and thus, electrical energy is generated.
An example of a positive active material for a secondary lithium battery is an oxide that includes lithium and transition metal and has a structure enabling intercalation of lithium ions. Examples of the oxide are lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and lithium nickel cobalt manganese oxide (Li[NiCoMn]O2, Li[Ni1-x-yCOxMy]O2).
For use as a negative active material, research into various carbonaceous materials including artificial and natural graphite, hard carbon, and non-carbonaceous material such as silicon (Si), which allow lithium ions to be intercalated and deintercalated, is being performed.
Non-carbonaceous materials show very high capacity density that is at least 10 times greater than that of graphite. However, due to volumetric expansion and shrinkage during charging and discharging of lithium, the capacity retention rate, charge/discharge efficiency, and lifetime characteristics of the non-carbonaceous materials may decrease.
Accordingly, there is a need to develop high performance negative active materials having improved capacity characteristics and ring lifetime characteristics.